In the semiconductor industry, various manufacturing processes are typically carried out on a workpiece (e.g., a semiconductor wafer) in order to achieve various results thereon. Processes such as ion implantation, for example, can be performed in order to obtain a particular characteristic on or within the workpiece, such as limiting a diffusivity of a dielectric layer on the workpiece by implanting a specific type of ion. Conventionally, ion implantation processes are performed in either a batch process, wherein multiple workpieces are processed concurrently, or in a serial process, wherein a single workpiece is individually processed. Traditional high-energy or high-current batch ion implanters, for example, are operable to achieve an ion beam-line, wherein a large number of wafers may be placed on a wheel or disk, and the wheel is spun and radially translated through the ion beam, thus exposing all of the surface area of the workpieces to the beam at various times throughout the process. Processing batches of workpieces in such a manner, however, generally increases the cost of the system, makes the ion implanter substantially large in size, and reduces system flexibility.
In a typical serial process, on the other hand, an ion beam is either scanned two-dimensionally across a stationary wafer, or the wafer is translated in one direction with respect to a generally stationary fan-shaped ion beam. The process of scanning or shaping a uniform ion beam, however, generally requires a complex beam-line, which is generally undesirable at low energies. Furthermore, uniform translation or scanning of either the ion beam or the wafer is generally required in order to provide a uniform ion implantation across the wafer. However, such a uniform translation and/or rotation can be difficult to achieve, due, at least in part, to substantial inertial forces associated with moving the conventional devices and scan mechanisms during processing.
Alternatively, in one known scanning apparatus, as disclosed in U.S. Patent Application Publication No. 2003/0192474, the wafer is scanned in two orthogonal dimensions with respect to a stationary “spot” ion beam, wherein the wafer is quickly scanned in a so-called “fast scan” direction and then slowly scanned in an orthogonal “slow scan” direction, thereby “painting” the wafer via a generally zigzag pattern. This two-dimensional scanning apparatus, however, utilizes direct drive actuators to linearly translate the wafer in the fast scan direction, wherein the transport velocity of the wafer in the fast scan direction is substantially limited due, at least in part, to significant inertial forces encountered during acceleration and deceleration of the wafer as the direction of fast scan transport is periodically reversed. Large inertial forces in the conventional apparatus are accordingly associated with a large reaction force at the direct drive actuator, wherein the large reaction force can ultimately lead to significant vibration of the apparatus, thus having a deleterious impact on the ion implantation process. Vibration may also pose a problem for nearby equipment, such as lithography equipment that is typically vulnerable to vibration. Furthermore, when the speed of the translation in the fast scan direction is limited in order to avoid vibration issues, process throughput can be deleteriously impacted.
Therefore, a need exists for a system and apparatus for reciprocally scanning a workpiece in two dimensions relative to an ion beam at substantially high speeds, wherein vibration from large inertial forces is mitigated, and wherein the scanning of the workpiece is controlled in order to uniformly process the workpiece.